gulpfile.js

// From https://rdyar.github.io/2016/03/25/gulp-file-for-jekyll-browser-sync/

var gulp        = require('gulp');
var browserSync = require('browser-sync');
var cp          = require('child_process');

var messages = {
  jekyllBuild: '<span style="color: grey">Running:</span> $ jekyll build'
};

/** * Build the Jekyll Site (windows) if you use Mac/Linux change jekyll.bat to just jekyll */
gulp.task('jekyll-build', function (done) {
    browserSync.notify(messages.jekyllBuild);
    return cp.spawn('jekyll', ['build'], {stdio: 'inherit'})
        .on('close', done);
});

/** Rebuild Jekyll & do page reload when watched files change */
gulp.task('jekyll-rebuild', ['jekyll-build'], function () {
    browserSync.reload();
});

/** Wait for jekyll-build, then launch the Server */
gulp.task('serve', ['jekyll-build'], function() {
    browserSync.init({
        server: "_site/"
    });
});

/** Watch all files for changes, except the _site and other unneccessary folders */
gulp.task('watch', function () {
    gulp.watch(['**/*.*', '!_site/**/*', '!node_modules/**/*','!.sass-cache/**/*' ], ['jekyll-rebuild']);
});

/**Default task, running just `gulp` will compile the jekyll site, launch BrowserSync & watch files. */
gulp.task('default', ['serve', 'watch']);